Recent years have seen an increase in environmentally sensitive power generation systems that generate power using natural energy. The natural energy includes sunlight, wind force, tide and the like. In a power conversion device or the like used in such a power generation system, a power semiconductor module is used. That is, the power semiconductor module is used in various environments. Accordingly, the power semiconductor module is demanded of, in addition to increased current and raised withstanding voltage, customizability corresponding to the usage, reduced space and the like.
Conventionally, the power semiconductor module included in the power conversion device is structured by one element for obtaining the target rated current. That is, as to the conventional power semiconductor module, it has not been contemplated using a combination of plurality of elements. Accordingly, as to the conventional power semiconductor module, out of a limited number of elements with which the rated current can be obtained, an element capable of obtaining the desired rated current is selected, and the element is put to use.
Therefore, the conventional power semiconductor module has various problems. The problems include, for example, a problem that space greater than necessary is required in the power conversion device in order to mount a heat dissipation plate inside that power conversion device. Further, the problems include, for example, a problem of poor heat dissipation property attributed to concentration of heat to a certain location in the power conversion device depending on the operation condition of the element.
In an attempt to solve such problems, a parallel-drive-type semiconductor module is coming into use. For example, Patent Document 1 discloses the technique of using a semiconductor module in which a plurality of switches are driven in parallel (hereinafter also referred to as the “related art A”). Further, Patent Document 2 discloses the technique of driving a plurality of semiconductor modules in parallel (hereinafter also referred to as the “related art B”).